222 STUDIES OF TREES 



small pores in the late wood, while running parallel with 

 the annual rings are little white lines such as are shown 

 in Fig. 149. These are lines of wood parenchyma. Wood 

 parenchyma is found in all woods, arranged sometimes in 

 tangential lines, sometimes surrounding the pores and 

 sometimes distributed over the cross-section. The dark, 

 horn-like portions of hickory and oak are the woodfibers. 

 They give the strength to wood. 



In many of the diffuse-porous woods, the pores are too 

 small to be seen with the unaided eye, and in some cases 

 they are not very distinct even when viewed with a magni- 

 fier. It is necessary to study such examples closely in 

 order not to confuse them with the woods of conifers. 



The woods of conifers are quite different in structure 

 from broadleaf woods, though the difference may not 

 always stand out prominently. Coniferous woods have no 

 pores, their rays are always narrow and inconspicuous, 

 and wood parenchyma is never prominent. The woods 

 of the pines, spruces, larches, and Douglas fir differ from 

 those of the other conifers in having resin ducts, Fig. 144. 

 In pines these are readily visible to the naked eye, appearing 

 as resinous dots on cross-sections and as pin scratches 

 or dark lines on longitudinal surfaces. The presence or 

 absence of resin ducts is a very important feature in identify- 

 ing woods, hence it is very important to make a careful 

 search for them when they are not readily visible. 



How to identify a specimen of wood: The first thing 

 to do in identifying a piece of wood is to cut a smooth 

 section at the end and note (without the magnifier) the 

 color, the prominence of the rays and pores, and any other 

 striking features. If the pores are readily visible, the wood 

 is from a broadleaf tree; if the large pores are collected in 

 a ring it belongs to the ring-porous division of the broadleaf 



